VSG60A Modulated Signal Power

With the VSG60A, I am using the Arb Modulation I/Q CSV option to modulate a 5.65 GHz signal to several time delayed pulses. When trying to verify the power of the pulsed signal, my spectrum analyzer and RF power meter read several dBm lower than what the VSG60 GUI is set to, even accounting for cable loss and attenuators. (When looking at the CW, the power measurements are spot on) Is there something I can do to on the VSG60 that will give me accurate power measurements.

rfong,

If you want to measure the power of a pulsed signal, I recommend using an AM vs time plot such as the one we provide in Zero-span, and using the marker to measure the power during the on phase of the pulse. If you need to use the standard sweep measurement, consider increasing the RBW to improve amplitude accuracy. In general unless the pulse width is as long as the spectrum analyzers acquisition length for a given IF, the amplitude will be lowered, since the acquisition will include both on and off portions of the pulse period. For an FFT based receiver such as ours, this means the signal will not be present for the full FFT, reducing the reported amplitude.

Regards,
Andrew

I measured the power of the pulsed signal from the VSG60 using the zero span mode of the BB60C spectrum analyzer and the BB60C reported that the power was more than 10dB more than what was selected on the GUI of the VSG60. When I tried measuring the power of another pulsed signal from a different signal generator, the power measurement on the BB60C was within 2dB of what was selected (most likely from cable loss).

However, I measured the power of both pulsed signals using the BB60C’s channel power option (with a measurement width of 50kHz and Max Hold), the BB60C’s measurement agreed with the VSG60’s GUI option over the other signal generator’s power (which was too low).

Which piece of equipment do I trust?

rfong,

Please email us at support@signalhound.com and we can assist you further. We can perform additional troubleshooting through email and help you determine if one of your devices is giving you invalid measurements.

Regards,
Andrew

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